Multimodal porogen platforms for calcium phosphate cement degradation

Calcium phosphate cements (CPCs) are widely used in orthopedic applications due to their biocompatible and injectable properties. Despite these advantages, CPCs face limitations in terms of poor degradability and insufficient macroporosity, which hinder effective bone regeneration. Previous studies have demonstrated that incorporating poly(d,l-lactic-co-glycolic acid) (PLGA) particles can improve macroporosity and enhance late-stage material degradation. However, the delayed degradation of PLGA, which typically begins after 2–3 weeks, poses a challenge for early-stage bone formation. This gap in understanding the temporal dynamics of porogen effects on CPC degradation and bone regeneration motivated further investigation into multimodal porogen systems.

This study aimed to address the limitations of calcium phosphate cements (CPCs) by exploring multimodal porogen platforms that combine early and late-stage porogens. The objective was to enhance CPC degradation and promote bone formation at both early and late stages. The researchers focused on using sucrose porogens for early pore formation and PLGA porogens for late pore formation. The study sought to evaluate the mechanical properties of CPC formulations, assess dynamic in vitro degradation, and analyze in vivo performance in a rat femoral bone defect model. By combining these porogens, the study aimed to overcome the delayed onset of PLGA degradation and improve overall material performance.

The study employed a multimodal porogen approach using sucrose and PLGA particles to modify calcium phosphate cement (CPC) formulations. The researchers first evaluated the mechanical properties of CPC by measuring compressive strength. They then conducted dynamic in vitro degradation experiments to observe the dissolution behavior of sucrose and PLGA particles over time. To assess the in vivo performance, the CPC formulations were implanted in a rat femoral bone defect model. The study also monitored crystal phase transitions during in vitro incubation and evaluated their impact on compressive strength. The combination of these methods allowed the researchers to analyze both the structural and functional properties of CPC under controlled and physiological conditions.

The addition of porogens to calcium phosphate cement (CPC) formulations resulted in a decrease in compressive strength across all tested formulations. However, the transition of the crystal phase during in vitro incubation was observed to increase compressive strength. Dynamic in vitro degradation experiments showed that sucrose porogens dissolved rapidly within one week, indicating potential for early pore formation. Despite this rapid dissolution, no significant additional effects on CPC degradation or bone formation were observed in the in vivo rat femoral bone defect model. The delayed degradation of PLGA porogens, which typically begins after 2–3 weeks, did not lead to enhanced bone formation in the early stages. The study also revealed that while sucrose dissolution occurred quickly, it did not significantly influence the overall degradation or regeneration outcomes in the in vivo setting.

The study's findings suggest that the use of multimodal porogen platforms combining sucrose and PLGA porogens does not significantly enhance calcium phosphate cement (CPC) degradation or bone formation in a rat femoral bone defect model. While sucrose porogens dissolved rapidly in vitro, this did not translate to improved outcomes in vivo. The delayed degradation of PLGA porogens, which begins after 2–3 weeks, did not lead to enhanced early-stage bone formation. The transition of the crystal phase during in vitro incubation was found to increase compressive strength, but this effect was not sufficient to overcome the limitations of porogen addition. The researchers propose that further investigation is needed to optimize porogen combinations and their temporal dynamics to improve CPC performance in bone regeneration applications.